allseason Posted May 16, 2011 Report Share Posted May 16, 2011 Is there a formula or calculation for the amount of vent opening needed out of the house/attic for a whole house fan? What is used as the basis as any unit that I have seen does not list any specs on a data plate, such as how much air they move per hour, etc. Link to comment Share on other sites More sharing options...
Mike Lamb Posted May 16, 2011 Report Share Posted May 16, 2011 It depends on how big the fan is (CFMs) to determine the NFVA. My whole house fan is 30†Link to comment Share on other sites More sharing options...
allseason Posted May 16, 2011 Author Report Share Posted May 16, 2011 Thanks Mike. I like the GAF dual fan that fits between the joists. Link to comment Share on other sites More sharing options...
Terence McCann Posted May 16, 2011 Report Share Posted May 16, 2011 I think the Grainger book has some fan information in them as well (not at home to look right now however). Link to comment Share on other sites More sharing options...
hausdok Posted May 16, 2011 Report Share Posted May 16, 2011 Hi, It really depends on your climate and what your state's energy code says - if you have one - and that's a moving target. Our 2006 Energy code had specific requirements shown at the table on page 8-5 of the code (http://www.energy.wsu.edu/Documents/Bui ... e-2006.pdf) but the new 2010 code, which went into effect on January 1st, has been gutted of those requirements. If any of you Washington State inspectors would like to download a copy of the 2010 Builder's Field Guide to the code, click here. ONE TEAM - ONE FIGHT!!! Mike Link to comment Share on other sites More sharing options...
allseason Posted May 16, 2011 Author Report Share Posted May 16, 2011 This fan has been in the house a long time, decades likely. I saw very little attic ventilation, far less than common sense and what the GAF specs call for. I need a rough idea to educate the buyer, which I can estimate from the information provided. Link to comment Share on other sites More sharing options...
Neal Lewis Posted May 16, 2011 Report Share Posted May 16, 2011 How 'bout take out the breeze conditioning and put in central air. Link to comment Share on other sites More sharing options...
allseason Posted May 17, 2011 Author Report Share Posted May 17, 2011 How 'bout take out the breeze conditioning and put in central air. That's the ultimate plan. Link to comment Share on other sites More sharing options...
airscape Posted July 13, 2011 Report Share Posted July 13, 2011 Use this formula, which is based on HVI-916 formula for NFVA CFM=NFVA (square feet) x 2432 x square root(P) where CFM= cubic feet per minute NFVA= net free ventilation area (sq. feet) P = pressure in inches of water column subsituting in P=.05, which is a safe value for maximum attic pressure: CFM=NFVA (square feet) x 2432 x square root(.05) More details here: http://blog.airscapefans.com/archives/homepower-article Link to comment Share on other sites More sharing options...
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